Single crystal boron carbide (B.sub.4 C) is a high temperature refractory material with a melting temperature in excess of 2,400.degree. C. The crystal structure of boron carbide is rhombohedral and consists of 12-atom icosahedral units located at corners of a rhombohedral unit cell connected by C--B--B or C--B--C chains lined along a cell diagonal (O. Chauvet, D. Emin, L. Forro, T. L. Aselage, and Z. Zuppiroli, Phys. Rev. B 53,14450 (1996)). The equilibrium compound in a B--C system is B.sub.4 C (ASM Handbook, Vol. 3, Alloy Phase Diagrams (edited by H. Baker), ASM International, Metals Park, Ohio (1992).) Other compounds within the system are generally regarded as solutions of boron in B.sub.4 C, or as solid solutions with carbon. Single crystal boron carbide has potential application in thermoelectric power conversion (C. Wood and D. Emin, Phys. Rev. B 29, 4582 (1984); C. Wood, D. Emin, and P. E. Gray, Phys. Rev. B 31, 6811 (1985).) A polaronic transport model has been developed to explain the thermoelectric conversion properties of single crystal boron carbide, where polaron hopping between icosahedra is phonon-assisted, or in other words, thermally activated (O. Chauvet, D. Emin, L. Forro, T. L. Aselage, and L. Zuppiroli, Phys Rev. B 53,14450 (1996); C. Wood and D. Emin, Phys. Rev. B 29,4582 (1984); C. Wood, D. Emin, and P. E. Gray, Phys. Rev. B 31, 6811 (1985); I. A. Howard, C. L. Beckel, and D. Emin, Phys. Rev. B 35, 2929 (1987); I. A. Howard, C. L. Beckel, and D. Emin, Phys. Rev. B 35,9265 (1987).) In light of the potential applications of boron carbide, it would be desirable to develop alternative methods of forming boron carbide crystals.